The transcription of human globin genes may involve the complex interaction of a variety of factors. The K562 human erythroleukemia cell line can serve as a model for the study of globin gene expression. The K562 cell line can be induced by hemin to accumulate embryonic and fetal hemoglobin, but not adult hemoglobin. It has been demonstrated that the beta-globin gene is intact but inactive in these cells. The cloned K562 beta-globin gene is expressed in COS cells and the transcriptionally inactive beta-globin gene in HEL cells is activated in MEL x HEL hybrids suggesting that the induction of beta-globin gene expression perhaps requires a specific transcriptional factor. The beta-globin gene promoter functions after microinjection into oocytes but not after transcription into HeLa or COS cells also suggesting that there might be transcriptional factors specific for embryonic genes. The current study assumes that induced K562 cells contain transcriptional factors specific for embryonic globin genes, which are absent or present only at low levels in uninduced K562 cells. We are preparing cDNA from the mRNA of induced K562 cells. The mRNA from uninduced K562 cells will be used to subtract the background corresponding to proteins present in both the induced and uninduced K562 cells. The remaining cDNA will be cloned into a vector (lambda gt10) to replicate enough copies for screening with mRNA or cDNA, from both the induced and uninduced K562 cells. Those cDNA clones wich are differentially expressed will be further characterized by transfecting back into K562 cells or other hemoglobin or non-hemoglobin producing cell lines, or by inserting into a protein expression vector (lambda gt11) so that the protein product can be examined.